GEOTHERMAL TECHNOLOGIES LEGACY COLLECTION - Bibliographic Citation


Bibliographic Citation


Full Text:
application/pdf
6 Mb

View Full Text Access Individual Pages  -   Search, view and/or download individual pages
Title: Multiparameter fiber optic sensing system for monitoring enhanced geothermal systems
Creator/Author: William A. Challener
Publication Date:2014 Dec 04
OSTI Identifier:OSTI 1056480
Report Number(s):DOE/EE0002787
DOE Contract Number:EE0002787
Document Type:Technical Report
Specific Type:
Coverage:Final
Resource Relation:
Other Number(s):
Research Org:General Electric Global Research
Sponsoring Org:USDOE; USDOE EE Office of Geothermal Technologies (EE-2C)
Subject:15 GEOTHERMAL ENERGY; 47 OTHER INSTRUMENTATION
Keywords:geothermal; EGS; enhanced geothermal systems; pressure; Raman DTS; Brillouin DTSS; Rayleigh COTDR; fiber optics; hydrogen darkening
Description/Abstract:The goal of this project was to design, fabricate and test an optical fiber cable which supports multiple sensing modalities for measurements in the harsh environment of enhanced geothermal systems. To accomplish this task, optical fiber was tested at both high temperatures and strains for mechanical integrity, and in the presence of hydrogen for resistance to darkening. Both single mode (SM) and multimode (MM) commercially available optical fiber were identified and selected for the cable based on the results of these tests. The cable was designed and fabricated using a tube-within-tube construction containing two MM fibers and one SM fiber, and without supporting gel that is not suitable for high temperature environments. Commercial fiber optic sensing instruments using Raman DTS (distributed temperature sensing), Brillouin DTSS (distributed temperature and strain sensing), and Raleigh COTDR (coherent optical time domain reflectometry) were selected for field testing. A microelectromechanical systems (MEMS) pressure sensor was designed, fabricated, packaged, and calibrated for high pressure measurements at high temperatures and spliced to the cable. A fiber Bragg grating (FBG) temperature sensor was also spliced to the cable. A geothermal well was selected and its temperature and pressure were logged. The cable was then deployed in the well in two separate field tests and measurements were made on these different sensing modalities. Raman DTS measurements were found to be accurate to ±5°C, even with some residual hydrogen darkening. Brillouin DTSS measurements were in good agreement with the Raman results. The Rayleigh COTDR instrument was able to detect some acoustic signatures, but was generally disappointing. The FBG sensor was used to determine the effects of hydrogen darkening, but drift over time made it unreliable as a temperature or pressure sensor. The MEMS sensor was found to be highly stable and accurate to better than its 0.1% calibration.
Publisher:
Country of Publication:US
Language:English
Size/Format:Medium: ED; Size: 6 MB
Rights:
Availability:
System Entry Date:2013 Mar 14
 View Non-Empty Fields Only

Top

Some links on this page may take you to non-federal websites. Their policies may differ from this site.